Adaptive Knee Brace Hinges with Dynamic Pivot Tracking
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Solution Overview
Problem
Existing knee brace hinge designs fail to accurately match the natural motion of the knee, leading to undesired forces and inadequate restraint against harmful motions, particularly at full extension where the ACL is vulnerable.
Innovation Solution
The knee brace hinges feature a dual-state mechanism with a constrained state providing one degree of freedom for rotation and an adaptive state offering three degrees of freedom, allowing the hinge to track natural knee motion while restraining harmful movements by using a combination of pivot and guide members interacting with cam slots to control rotational and translational movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed pivot point hinge design is used, then the hinge structure is simple and provides stable restraint, but the hinge cannot accurately track the varying natural motion of the knee
Solution Approach 1:
The hinge transitions from a fixed pivot point to a dynamic floating pivot point that moves anterior-posterior and superior-inferior to track the instantaneous center of rotation of the knee. This dynamic adaptation allows the hinge to follow natural knee motion while maintaining restraint capability through controlled degrees of freedom
Solution Approach 2:
The hinge is divided into multiple components including a cam mechanism with cam slot, guide members, and pivot members that work together to achieve independent anterior-posterior and superior-inferior movements of the pivot point, allowing complex motion tracking through coordinated simpler elements
2Adaptability or versatility
If a floating pivot point hinge with multiple degrees of freedom is used, then the hinge can track natural knee motion, but the hinge becomes unable to restrain harmful motions
Solution Approach 1:
The hinge provides different degrees of freedom in different regions of motion: full floating pivot capability (2 degrees of freedom) in the flexion range where natural motion varies, and constrained pivot movement in the extension range where harmful motions must be restrained, achieving location-specific functional optimization
Solution Approach 2:
The hinge dynamically adjusts its degrees of freedom based on knee position: the cam mechanism allows anterior-posterior pivot movement during flexion to track natural motion, while limiting pivot movement during extension to prevent harmful motions, making the restraint capability adaptive rather than static
3Reliability
If a hinge with constrained pivot movement is used, then the hinge can restrain harmful motions, but the hinge applies undesired forces to the knee due to motion mismatch
Solution Approach 1:
The hinge uses a dynamic cam mechanism that allows the pivot point to move anterior-posterior and superior-inferior based on knee flexion angle, matching the natural trajectory of the instantaneous center of rotation and eliminating undesired forces caused by motion mismatch
Solution Approach 2:
The hinge changes the positional parameters of the pivot point dynamically during knee motion, allowing anterior-posterior and superior-inferior displacement to follow natural knee kinematics, thereby reducing harmful forces while maintaining restraint when needed
Data Source
AI summary
The disclosed knee brace hinges enable a knee brace including the hinges to track the natural motion of the brace wearer's knee while restraining the knee from harmful motions. In certain embodiments, in a first range of motion the hinges have only one degree of freedom, rotation about a fixed axis. In a second range of motion, the hinges have at least two degrees of freedom, rotation and translation.